Physical activity is a complex, multidimensional exposure that is difficult to measure validly among free-living individuals, and improvements in physical activity assessments are needed to more precisely characterize physical activity in relation to cancer outcomes. With improvements in physical activity assessments, more precise estimates of physical activity and perhaps stronger associations might be seen, which will ultimately help determine whether decreased fitness or increased fatness is the main predictor of cancer risk. Previous studies have examined the metabolic effects of energy imbalance on various biological parameters putatively related to carcinogenesis, and have explored the relations of these factors to cancer risk. The current research project is intended to add to this research by focusing on certain inflammatory cytokines (CRP, IL-6, TNF-alpha), growth factors and their major binding proteins (IGF-1 and IGFBP-3), steroid hormones (testosterone, estrogen, SHBG), and energy balance-related genes in relation to cancer. Each study participant will undergo: (1) a one-time blood draw at the beginning of the study; (2) the administration of a newly developed physical activity questionnaire at the beginning of the study and a re-administration of the same questionnaire one year later; (3) four 7-day physical activity assessments using motion sensors spaced between the two physical activity questionnaires; (4) a one-time measurement of physical fitness at the end of the 1st motion sensor test. Study subjects will be monitored with accelerometers and physical activity records simultaneously. The devices will be worn at all times for 7 consecutive days, except for sleeping, showering, and swimming. Subjects will be instructed to record the time of day they wake up and go to bed, to note the times the devices are put on and taken off, and to not change their usual level of physical activity during the time period they are monitored. To account for systematic variation in physical activity levels due to season of the year, all measurements will be conducted during four periods throughout the year, one in each season. Compliance will be verified by systematically examining accelerometer and pedometer counts for missing data, defined as continuous periods of 2 or more hours with no recorded movement during daytime hours. A comprehensive physical activity questionnaire will be administered and results will be expressed as METs. The Actigraph accelerometer will be used to quantify the amount of body movement continuously. The monitor will be worn on the right hip of the participant in the anterior axillary line. The device consists of an accelerometer and a data storage unit for on-line registration, processing, and storage of acceleration signals. The accelerometer comprises three uniaxial piezoresistive accelerometers and registers accelerations in three orthogonal directions during body movements. Acceleration signals are processed to obtain the sum of the rectified and integrated acceleration data from all three measurement directions. The final output is expressed as counts per minute. While being monitored, subjects will be requested to keep a physical activity record with the intention of capturing all sources and patterns of physical activity throughout the day. Participants will be instructed to enter items regarding specific types, frequency, duration, and intensity of activities performed. Physical activity records will be completed by participants each night before going to bed. Laboratory analyses of CRP, IL-6, and TNF-&#61537; will be conducted usingt standard methodology.